Arrangement for fuel injection in a free-piston unit



Feb. 8, 1949. E, rrzL 2,461,223

ARRANGEMENT FOR FUEL INJECTION IN A FREE-PISTON U NIT Filed Aug. 23, 1944 3 Sheets-Sheet l N m R J 8 i i to N i 3; o o e 0 0) 0 D o a) 0 0 c 0 N v o 0) c 0 o w 2 I 2; m I I r 3 5 v v v q O) O (0 O C 7' 0 0 N o: o w 0 O f 8 3 2 N v i 8 INVENTOR Feb. 8, N 1949.

D. E. MEITZLER ARRANGEMENT FOR FUEL INJECTION IN A FREE-PISTON UNIT Filed Aug. 23, 1944 3 Sheets-Sheet 2 m T. N w N U: W 0+ vm 2 mm mm N w No m2 m2 9mg m\- wmr I \\U\ Feb. 8, 1949. n'z 2,461,223

ARRANGEMENT FOR FUEL INJECTION IN A FREE-PISTON UNIT Filed Aug. 23, 1944 5 Sheets-Sheet 3 FIG. 4

INVENTOR Patented m. s, 1949 ARRANGEMENT FOR FUEL INJECTION IN A FREE-PISTON UNIT Donald E. Meitzler, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 23, 1944. Serial No. 550,895

Claims. (Cl. 230-56) This invention relates to an injection system for free-piston units and particularly to -an arrangement by which the system may be filled with fuel prior to starting the unit.

Starting a free-piston unit having opposed pistons reciprocating in an engine cylinder may be effected by moving the pistons into starting position in which they are spaced from the inner end of the piston stroke and then causing the pistons to move rapidly toward each other on a starting stroke tov cause compression ignition of the fuel injected into the cylinder during the starting stroke. To assure satisfactory fuel injection the injection system, which is generally actuated by the restraining linkage which connects the pistons, must be filled with fuel prior to the starting stroke. A feature of this invention is an arrangement by which to assure filling of the injection system.

The injection pump may be the type in which the pump plunger closes the filling and relief ports during the pumping stroke in order to trap in the cylinder fuel to be pumped to the nozzle. A feature of this invention is the arrangement of the starting system so that when the pistons are in starting position the filling port will be uncovered and the injection system will fill with fuel.

If the injection system is the accumulator type the pump plunger may have a venting groove which connects the accumulator chamber to a vent port in one position of the plunger to assure removal of all air from the chamber. A feature,

of the invention is the arrangement of the pump and starting system so that the accumulator chamber is vented while the pistons are in starting position.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 11s a sectional view through the free-piston unit.

Fig. 2 is a sectional view'of the restrainin linkage showing the cam for actuating the injection pump. 1

Fig. 3 is a sectional view of a part of the starting system.

. Fig. 4 is a sectional view of the injection system.

Fig. 5 is a sectional view of the injection system with the plunger in another position, and showing the actuating means.

The unit shown includes an engine cylinder to having reciprocating pistons l2 and Il to plete the reciprocating piston assemblies.

which compressor pistons I6 and I8 in cylinders 20 and 22 are integrally connected. Sleeves 24 and 26 attached to the compressor pistons com- The sleeves in combination with stationary pistons 28 and 30 form air spring cylinders.

' i The piston assemblies are moved apart by the burning of fuel injected into engine cylinder it through one or more nozzles 32. Air compressed in the air spring cylinders on the power stroke returns the piston assemblies. The assemblies are always maintained at equal distances from the center of the engine cylinder by linkage, Fig. 2. which may include racks 34 and 3t-extendina from the piston assemblies and meshing with a pinion 38 on a shaft Ml.

Intake manifold 42 which extends around the compressor and engine cylinders conducts air to intake valve 44 in the heads of the compressor cylinders through which air alternately enters opposite ends of the cylinders. The compressed air leaves the cylinders through discharge valves 46, also at opposite ends of the compressor cylinders, and passesinto a central scavenge chamber 48 and end chamber 50 and 52. These chambers may be interconnected by a scavenge manifold, not shown.

Compressed gas from the scavenge chambers enters engine ports 54 and 56 which are uncovered by pistons i2 and It at the end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas in the engine cylinders is discharged through exhaust ports 58 into exhaust manifold oil.

The injection device is actuated from a cam 62, Figs. 2 and 5, on the same shaft 40 that carries the pinion 38. A shoe engages cab 62 and is mounted in a block to movable between guides 88. Block 66 engages the end of a plunger l0 reciprocating in a bore 12 in a casing l5. With the plunger in the position shown in Fig. 5 before it begins its injection stroke, an inlet port 16 admits fuel to the end of bore l2. During the. injection stroke the plunger closes port it and fuel is forced by the plunger into accumulator chambers 18 and 80, Fig. 4, through a groove 82 in a valve 83 and a cross passage 86 which connects the chambers. Valve 84 is slidable in a bore 88 in a ring 90 in the casing. e

of the valve during the injection stroke oi the plunger. Groove 82 permits a throttled flow of fuel past the valve into the accumulator chambers. The end of valve 84 remote from seat 96 engages a seat 98 at the end of bore 08 to close the end of groove 82.

Air in the accumulator chambers I8 and is vented through a passage I00 in casing III which connects with the upper end of chamber IS. The opposite end of the passage forms a port I02 in bore I2 opposite a relief or vent port I04; Plunger has a groove I06 which at a predetermined point during the plunger stroke connects ports I02 and I04 so that air in the accumulator chambers 18 and 80 is discharged through passage I00. Discharge of fuel through passage 82 to nozzle 32 may be controlled by a check valve I08 held against a seat H0 by a spring II2. When accumulator valve 84 moves to open passage 92 fuel pressure opens the check valve I00 and flows through a groove II4 to one or more openings I I6 in the end of nozzle 32.

During the pumping stroke of the plunger the the head of the plunger closes inlet port 16 and port I02 is closed by the edge of groove I06. As the plunger continues its pumping stroke with port I6 closed the pressure of fuel in chambers I8 and 00 is raised until port I6 is uncovered by groove I06. Fuel from the space at the head of the plunger is then discharged through a passage II 8 in the plunger extending from the head of the plunger to groove I06. The resulting reduction of pressure in the plunger bore causes valve 84 to move endwise into the position of Fig. 4, thereby opening passage 92 for the discharge of fuel from the accumulator chambers through the nozzle. Accumulator valve 84 is again moved to engage seat 96 when the plunger begins its next pumping stroke.

During the return stroke of plunger I0 groove I06 connects ports I02 and I04 and the pressure remaining in chambers 18 and 00 forces out through passage I 00 any air that may have been trapped in the chambers.

In order that the above described injection system may be entirely filled with fuel before the free-piston unit is started, the starting system is arranged so that when the pistons are moved into starting position the plunger I0 will have been moved into the position shown'in Figure 5 in which port I6 is uncovered and ports I02 and I04 are connected so that fuel may flow through the pump to fill the accumulator chambers, the latter being vented to permit escape of any air therein. As shown in Fig. 3 the starting system includes an arrangement by which the pistons may be moved substantially into the position of Figures 1 and 3 adjacent the outer end of the piston stroke. The piston moving means is shown in Figure 3 for the piston assembly inciudingthe compressor piston I6. A similar piston moving means would be provided for the other piston assembly.

Extending from piston I6 are spaced tubes I20 and I22 forming at their outer ends an annular plunger I24 fitting between stationary spaced tubes I26 and I28. The stationary tubes are supported in a block I30 which may be integral with a part of the wall of the central scavenge chamber 48. Gas under pressure is admitted to the space between the tubes I26 and I28 through a passage I32 and a connecting conduit I34. This fiuid acts on plunger I24 to move thepiston I6 into the position shown. The position to which the piston is moved is determined by a vent I36 stopped with the pistons in provided in tube 126 so that the piston assembly will not be moved further toward outer end position than the position shown in Figure 3.

, cam 62 for the fuel injection device will be in the position of Figures 2 and 5 so that the fuel may enter port 16 and fill the entire accumulator system. The remainder of the starting system, which not being a part of the invention is not shown, may be the type described in the copending application of Meitzler, Serial No. 495,927, filed July 23, 1943, now patent No. 2,439,482, or in the copending Cooper application Serial No. 550,875, now patent No. 2,434,453. Dot-dash lines I38, Fig. 2, and I40. Fig. 5, represent similar positions of cam 62 in the two figures.

In operation, the free-piston unit having been any position, gas under pressure is supplied to passage I32 thereby acting on plunger I24 and moving the piston assemblies into the position shown in Fig. 1. Fuel under pressure is supplied to filling port 16 and when the piston assemblies reach the positions shown, the linkage shown in Fig. 2 will have moved cam 62 into the position of Fig. 5 allowing plunger I0 to reach the position of this figure in which filling port I6 is uncovered by the end of the plunger and vent port I04 is connected by groove I06 with passage I00. Fuel under pressure thus enters the bore 12 through port I6 to fill said bore. Fuel from the bore flows past valve 84 into chambers I8 and 80, and any air in the chamber is forced out through passage I00, the passage 04 entering, as above stated, the upper end of the chamber I8. The fuel pump is thus filled with fuel, and when the piston assemblies are moved together by the starting system, on the starting stroke, the fuel will be injected through the nozzle 32 into the engine cylinder. With a delivery of fuel assured on the starting stroke, the free-piston unit will start dependably on the first operation of the starting system.

'It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

Iclaim:

1. A free-piston unit including, a piston, an engine cylinder in which the piston reciprocates, pump means responsive to the piston reciprocation for supplying fuel to said engine cylinder, said pump means including a casing having a filling port, a plunger reciprocating in said casing and movable in response to reciprocation of the piston for covering and uncovering the port, said engine piston having a starting position from which it is moved in starting the unit, and means interconnecting said piston and the plunger by which the plunger is reciprocated, said interconnecting means supporting the plunger in a position to uncover said filling port when the piston is in starting position, in combination with a starting system and means forming a part of said system for moving said piston into said starting position.

2. In a free-piston unit, a piston, an engine cylinder in which the piston reciprocates, pump means responsive to the piston reciprocation for supplying fuel to said engine cylinder, said pump means including a casing having a filling port communicating with a fuel supply, and a plunger covering said port during a part of its stroke,

and connected to and movable in response to menses 3. In aifree-piston unit, a piston, an engine cylinder in which the-piston reciprocates, pump means responsive to the piston reciprocation for supplying. fuel to said engine cylinder, saidpump means including a casing having a filling port,

and a plunger movable in response to pistonmovement and uncovering said port during a part of its stroke, an accumulator chamber into which fuel under pressure is pumped by said plunger, said plunger also having means for venting air from they chamber during the part of the stroke when the filling port is uncovered, in combination with a starting system and means forming a part of said system for moving said piston into a position to cause the plunger to move to a position to uncover the filling port and to vent said chamber'prior to starting the unit.

4. Ina free-piston unit, a piston, an engine cylinder in which the piston reciprocates, pump means responsive to the piston reciprocation for supplying fuel to said engine cylinder, said pump means including a casing, a plunger reciprocating in said'casing. said casing having a filling port connected to a fuel supply, and an accumulator chamber into which fuel under pressure is pumped by said plunger, said plunger having means for venting air from said chamber'in one part of its stroke, in combination with 'a starting system, and means forming a part of the starting system for moving said piston into a starting position and thereby moving the plunger into a position in which the chamber is rented.

5. A-free-piston unit having opposed pistons, an engine cylinder in which the pistons reciprocate. a linkage connecting the pistons, pump means including a casing, a reciprocating plunger in said casing actuated fromsaid linkage for supplying fuel to said engine cylinder, said casing having a filling port connected to a supply of fuel, and a vent port both adapted to be uncovered during a part of the plunger stroke to permit the filling of the pump and the escape of air in the pump, said pistons having a starting position from which they are moved in starting the unit, said linkage, when the pistons are in starting position, causing the plunger of said pump means to assume a positionin which the ports are uncovered so that the-Dump may be automatically filledwith fuel and the air vented therefrom, in combination with a starting system and means forming a part of the system for moving said pistons automatically to said starting position.

nsrannucns crrsn The following references are of record in the file of this patent:

UNITED STATES PATENTS 2,308,978 Pateras-Pescara Dec. 29, 1942 DONALD E. MEITZLER. 

